You may be able to via an App like Fring. It uses WiFi to make calls to IM User clients like MSN and Google Talk. Try it out. I would be intrested to know if this works. I used the Pre-release of Fring on my iPhone and it worked. Although a bit weak. When the Full Version is released it may work better.

Update,

On further thought.. I do think the Touch has a Microphone for voice. Or does it?

You may be able to via an App like Fring. It uses WiFi to make calls to IM User clients like MSN and Google Talk. Try it out. I would be intrested to know if this works. I used the Pre-release of Fring on my iPhone and it worked. Although a bit weak. When the Full Version is released it may work better.

Update,

On further thought.. I do think the Touch has a Microphone for voice. Or does it?

your friend may be completely stupid, but there is a microphone available for the iTouch and also software that allows for VoIP. Essentially that makes phone calls, but you do have to be using WiFi and you do have to buy (or build) the microphone.